Gear pump



Dec. 23, 1952 J. P. JOHNSON GEAR PUMP 4 Sheets-Sheet 1 Filed Feb. 18, 1946 INVENTOR.

JAMES R JOHNSON ATTORNEYS Dec. 23, 1952 J. P. JOHNSON GEAR PUMP 4 Sheets-Sheet 2 Filed Feb. 18, 1946 INVENTOR.

JAMES P.JOHNSON ATTORNEYS Dec. 23, 1952 J. P. JOHNSON 2,622,534

GEAR PUMP Filed Feb. 18, 1946 4 Sheets-Sheet 3 3| n "lll 4 nvmvrm JAMES P. JOHNSON ATTORNEYS J. P. JOHNSON Dec. 23, 1952 GEAR PUMP 4 Sheets-Sheet 4 Filed Feb. 18, 1946 INVENTOR.

JAMES P. JOHNSON ATTORNEYS Patented Dec. 23, 1952 UNITED STATES PAENT QFFIQE GEAR PUMP .iames P. Johnson, Shaker Heights, Ohio Application February 18, 1946, Serial No. 648,229

11 Claims. l

This invention relates to improvements in gear pumps and has for its principal object the provision of a pump wherein the gear containing cavity within the body portion need not be closely fitted to the gears. At present, gear pumps of the simpleststructures must have a gear containing cavity which is rather closely fitted to the periphery and side faces of the gears. Such structures present the further problem in that where light weight pumps are desirable, as in aircraft, the differences in coefficients of thermal expansion of the various metals used cause improper functioning of the pump at the temperature extremes. Thus, where the pump includes aluminum alloy body portions and hardened and ground steel gears, a properly fitted cavity and gear assembly at room temperature will be apt to seize at temperatures of 60 F. and will be loose and inemcient at temperatures of +150 F.

It is, therefore, another object of this invention to provide a gear pump of light weight construction in which the parts that are closely fitted to the gears are made of metals having the same coeflicient of thermal expansion as that of the gears.

Another object of this invention is to provide a simple limiting means for positioning the parts relative to the gears to avoid the possibility of binding contact occurring between them.

Another object is to provide novel means for automatically moving the closely fitted parts and gears relative to one another to avoid overloading of the pump, such means being operative when the pressure of the fluid being discharged by the pump attains a predetermined maximum.

Another object is to provide novel means for manually unloading the pump.

Another object is to provide means closely fitted to the gears which can be readily replaced without disassembling the pump.

Another object is to provide means which have flexible portions thereon capable of being yieldably moved closer to the side faces of the gears by fluid pressure to enable the pump to be used at higher pressures.

Additional objects and advantages of the invention shall become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, said invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which th rinciple of the invention may be employed.

In the drawings:

Fig. 1 is a cross sectional view through the gears and drive shaft of one form of pump;

Fig. 2 is a cross sectional view taken along line 2-2 of Fig. 1;

Fig. 3 is an end elevation of the pump shown in Fig. 1 as viewed from the left-hand end of Fig. 1;

Fig. 4 is a cross sectional view taken along line 4-4 of Fig. 2;

Fig. 5 is a perspective view of a shroud or sleeve member which is fitted into the pump cavity;

Fig. 6 is a cross sectional view through the gears and drive shaft of a pump similar to that shown in Fig. 1 but including in addition thereto means for automatically limiting the pressure delivered by the pump;

Fig. 7 is a cross sectional view taken along line 'l-l of Fig. 6;

Fig. 8 is a cross sectional view taken along line t3 of Fig. 6;

Fig. 9 is an end elevation of the pump shown in Fig. 6 as viewed from the right-hand end of Fig. 6;

Fig. 10 is a cross sectional view of a pump similar to that of Fig. 1 but including means for automatically limiting the pressure delivered by the pump;

Fig. 11 is a plan View of the pump shown in Fig. 10;

Fig. 12 is a cross sectional view of a modified form of means for automatically limiting the pressure delivered by the pump;

Fig. 13 is a cross sectional view of a pump having a modified form of shroud or sleeve member;

Fig. 14 is a cross sectional view taken along line Mli of Fig. 13;

Fig. 15 is a cross sectional view of a pump having manually operated means for limiting the pressure delivered by the pump; and

Fig. 16 is a plan view of the pump shown in Fig. 15.

Referring now to the drawings and first generally to all of the forms shown. In the following general description, like parts are designated by like numerals. Each pum comprises body portions I and 2 between which is defined a cavity of oblong shape. Rotatably mounted within this cavity is a driving gear 3 and a driven gear 4, each of which is preferably hollow to decrease the weights thereof. Each gear is provided with projecting stub shafts integral therewith which are rotatably mounted in bushings 5 and 6 in each body portion I and 2. Body portions I and 2 are preferably made of aluminum alloy for air craft pumps, but obviously other materials could be used where saving in weight is not critical. Gears 3 and 4 are preferably made of hardened and ground steel and the bushings 5 and 6 are preferably made of a bearing material such as bronze. Gears 3 and 4 are in mesh with one another in said cavity and the teeth thereof are accurately formed in order that the teeth of one gear intermesh with the teeth of the other gear in substantially sealed relationship. Body I is provided with inlet and discharge ports in communication with said cavity. The inlet port is in the form of a shroud or sleeve member I which has a central passage 8 therethrough and an inner portion extending into said cavity. Passage 8 is made as large as possible commensurate with the size of the pump to provide a large inlet chamber to minimize cavitation which would occur if fluid were drawn into the cavity at high velocity. Shroud 7 has a face 9 which comprises two merging cylindrical portions having their axes coincidental with the axes of rotation of the gears 3 and 4. Face 9 is disposed in close proximity to the peripheries of the gears 3 and 4.

In fact, it is desirable that there be no clearance between face 9 and the peripheries of the gears so that a fluid tight seal will be formed therebetween. However, in actual practice, it is necessary to provide a very slight clearance so that the gears can rotate freely. Face 9 extends about the periphery of each gear for a distance at least equal to the pitch of the teeth of the gear in the case of spur gears. But obviously, if the gears are provided with helical teeth or herringbone teeth, the minimum distance that face 9 should extend about the periphery of the gears is an amount such that the space between successive teeth is not at any time in communication with both the inlet port and the discharge port.

In the forms of shroud 7 shown in Figs. 2, 5, 8, 10, 12 and 15, the inner end thereof is also provided with spaced lip portions It, the inner surfaces II of which are disposed in close proximity to the side faces of each of the gears. As pointed out in connection with the face 9, these surfaces 1 I are preferably so close to being in contact with the side faces of the gears as to form a seal therewith, but not actually in binding contact so as to impede free rotation of the gears. The lips IE! are preferably of such thickness and fitted into the cavity defined between body portion I and 2 with sufficient clearance that fluid under pressure acting on the outer surfaces I2 thereof will flex the lips closer to the side faces of the gears as the pressure increases. In this way the pump can effectively be used for higher pressures than would be possible if the lips it! were rigid and spaced from the side faces of the gears a fixed distance. From the foregoing description, it is apparent that the seal formed between the peripheries and side faces of the gears and the shroud I and between the gears where in meshed relation divides the cavity into two separate chambers which are out of communication with one another. The lips I 0 are preferably cut away as at I3, so as to partially encircle each of the bushings 5 and B.

In the form of shroud 1' shown in Fig. 13, there are no lips I0 and therefore the cavity defined by the body portions I and 2 must be of such thickness as to be in close proximity to the side faces of the gears in order that the two distinct chambers be formed. In all of the forms described above, except as noted in connection with that of Fig. 13, the cavity defined by the body portions need not be closely fitted to the gears and may be spaced at considerable distance therefrom as far as length, width and thickness are concerned. Thus, it is immaterial whether or not the coefficients of thermal expansion of the body portions and the gears are the same.

To eliminate the possibility of binding contact between the face 9 and the periphery of gears 3 and 4, the shroud I and body portion I are provided with shoulder portions I4 which, when engaged, preclude further movement of face 9 toward the gears. This shoulder contact establishes a minimum clearance space between face 9 and the gears.

While the driving means and the seal therefor form no part of this invention, such will now be briefly described with particular reference to Figs. 1 and 6'. In Figs. 1 and 6, a drive shaft I5 is rotatably supported in body portion 2. The inner end of drive shaft I5 is provided with a spline engaged in driving relation with a splined opening in driving gear 3. Drive shaft I5 is provided with a sleeve I6 fixed longitudinally thereof and having a flanged portion thereof in sealing engagement with an end face of a sleeve H. An adaptor I8 is threaded into said body portion 2 and is provided with a finger I9 engageable in any of several spaced slots 20 in the body to lock said adaptor in said body. Between the inner end of adaptor I8 and sleeve I? is a sealing ring ZI of rubber or rubber-like material. A spring pressed ball 22 normally urges the drive shaft l5 toward the left to establish a seal between sleeves Hi and I! and between sleeve I? and adaptor I8. A passage 23 between the inlet port and the driving mechanism prevents pressure from building up in the drivin mechanism.

The theory of operation of gear pumps is well known to those skilled in the art so let it suffice for the purposes of this disclosure to state that the rotation of driving gear in a counter-clockwise direction as viewed in Figs. 2, 7, 1O, 12, 13 and 15 causes rotation of driven gear 4 in a clockwise direction and thus the teeth coming out of mesh or out of engagement with one another will create a displacement volume to draw fluid into the inlet chamber and conversely, the teeth which are coming into engagement will squeeze out fluid and discharge the same from the discharge chamber.

Having now described the construction which is common to the various forms of this invention, reference will now be made to certain figures in which are shown certain other features. In the structure shown in Figs. 6-9, there is provided a fluid pressure responsive means for automatically creating a space between the face 9 of shroud I and one of the gears when the pressur being delivered by the pump attains a predetermined maximum. The means for accomplishing this comprises rotatably mounted bushings 55 and 56 in which the driven gear stub shafts are rotatable, a gear 24 connected to said bushings 55 and 56, and a reciprocably mounted rack 25 engageable with said gear 24. As clearly shown in Fig. 7, bushings 55 and 58 are rotatable about an axis eccentric of the axis of rotation of gear 4. Gear 24 is connected to bushings 55 and 56 by means of a squar shaft 26 in engagement with square holes in the bushings. Rack 25 has a spring 28 associated therewith for holding it in the position shown in Fig. 8. When the rack 25 is in the position shown in Fig. 8, the

bushings 55 and 56 bear relation to the gear 4, as shown in Fig. 7. The end portion of rack is cylindrical and is fitted into a bore which, by means of passage 21, is in communication with the discharge chamber of the pump. In normal operation of the pump, the various parts thereof will bear relation to one another as shown in Figs. 6, 7 and 8. However, should th pressure of the fluid in the discharge chamber exceed a predetermined maximum, the force of such pressure will move rack 25 upwardly as viewed in Fig. 8 and in so doing, will effect rotation of gear 24 and thus the bushings 55 and 56 in a counterclockwise direction, as viewed in Fig. '7. Such rotation of bushings 55 and 56 moves driven gear 4 away from driving gear 3 and also away from the face 9 of the shroud 1, thereby effecting communication between the discharge and inlet chambers to prevent further increase of the pressure in the discharge chamber. If desired, adjusting means could be provided for the spring 28 so that the relief or unloading of pressure could be varied. To hold gear 24 and square shaft 25 from longitudinal movement, a spring pressed plunger 29 is provided. This plunger 29 is provided with lip portions thereon in engagement with the side faces of gear 24.

In Figs 10 and 11 there is shown a fluid pressure responsive means Which automatically moves the shroud 1 away from the gears 3 and 4 when the pressure being delivered by the pump exceeds a predetermined maximum. This means comprises a piston rod 3|] which is reciprocably mounted in a bore in the body portion I. A passag 3| affords communication between the end of the piston rod 3!) and the discharge chamber of the pump. A spring 32, in engagement with piston rod 30, normally holds the piston rod in its lowermost position as shown in Fig. 10. A forked lever 33 is pivotally connected to the end of the piston rod. Th forked end of lever 33 is pivotally connected to a link 34 which link ispivotally connected to the body portion l. Shroud I is provided with a groove 35 in which pin portions 36 of the forked lever 33 are engaged. Inasmuch as the piston rod 39 is constrained to move in a straight line, the forked lever 33 and link 34 which are pivotally connected to one another and to the piston rod and to th body, respectively, will maintain an in line relationship permitted by the slight looseness at the pivot points. When the fluid pressure in the discharge chamber acting on the end of piston rod 30 exceeds the force exerted by spring 32, piston rod 30 will move upwardly and as a consequence, shroud I will be lifted upwardly and face 9 thereof will be pulled away from the periphery f gears 3 and 4. Movement of the face 9 away from the periphery of the gears effects communication between the discharge chamber and the inlet chamber and thus th pressure which can be delivered by the pump is limited.

In Fig. 12, the shroud I is directly spring loaded by a spring 38 which normally holds the shoulders id in engagement and therefore face 9 of the shroud in proper relation to the periphery of the gears. A passage 4D affords communication between the discharge chamber and shoulder 14 of the shroud. To assure that fluid pressure will react against substantially the whole extent of shoulder i l, a recess I3! is provided, which communicates with passage 49. When the pressure of the fluid in the discharge chamber builds up to a predetermined maximum, such pressure will react between shoulders i4 and force the shroud upwardly to move face 9 thereof away from the periphery of the gears and thereby create a bypass passage which is efiective to limit the maximum pressure which can b delivered by the pump. As in the other forms wherein springs are shown, adjusting means could be utilized, if desired, to vary the spring tension and therefore the pressure deliverableby the pump.

In Figs. 15 and 16, there is included a forked lever 4i pivotally connected intermediate its ends to the body portion l. The forked end of lever A! has pin portions :55 thereof in engagement with a groove 42 in the shroud I. The opposite end of lever 4| is provided with a cam member 43 which is pivoted thereto and in engagement with body portion i. A spring 44 bears against the body portion I and engages forked lever 4! so as to tend to normally mov said forked lever ii in a direction to move the shroud away from the gears. When cam member 43 is rotated in a clockwise direction, the cam surface thereof is moved away from the body portion I to permit spring 44 to pivot the fork lever 4| and thereby move the shroud away from the gears. Movement of the shroud away from the gears unloads the pump. With this structure, it is possible to unload the pump at will at any desired pressure.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I therefore particularly point out and distinctly claim as my invention:

1. In a gear pump, a body provided with a cavity therein and an inlet port and an outlet port leading into said cavity, two gears in mesh mounted for rotation within said cavity, and a unitary insert independent of said body provided with a passage therethrough constituting such inlet port and with a face thereof including cylindrical portions in close proximity to the peripheries of the respective gears and extending thereabout for a distance at least equal to the pitch of the teeth of said gears whereby to form with said cavity and said gears two independent chambers respectively communicating with said ports, at least one of said gears being mounted for movement transversely of its axis away from the portion of said face in close proximity therewith to establish direct communication between such chambers through the space thus formed between such portion of said face and the periphery of the movable gear.

2. A pump according to claim 1 further characterized in that fluid pressure responsive means are operatively connected to said movable gear to move said gear away from such portion of said face when fluid at a predetermined pressure is applied to said fluid pressure responsive means.

3. A pump according to claim 1 further characterized in that means are provided for moving said movable gear which comprises a bushing engageable with said gear and rotatable about an axis eccentric thereto, a third gear having a nonrotatable connection within said bushing, and a reciprocably mounted rack in mesh with said third gear, said rack having a portion thereof exposed to fluid under pressure delivered by the pump and being movable in one direction by fluid under pressure applied thereto whereby to rotate said third gear and thus said bushing to move said movable gear.

4. In a gear pump, a body provided with a cavity therein and an inlet port and an outlet port leading into said cavity, two gear members in mesh mounted for rotation within said cavity, a third member independent of said body provided with a passage therethrough constituting such inlet port and with a face thereof including cylindrical portions in close proximity to the peripheries of the respective gear members and extending thereabout for a distance at least equal to the pitch of the teeth of said gear members whereby to form with said cavity and said gear members inlet and discharge chambers respectively communicating with said ports, one of said members being movable along a path transverse to the axis of one of said gear members, and fluid pressure responsive means operatively connected with said movable member to move said members relative to one another to form a leakage space between such face and at least the peripheral portion of one gear member and thus establish direct communication between such inlet and discharge chambers, said fluid pressure responsive means being exposed to fluid under pressure delivered by said pump and operative to move said members as aforesaid when such fluid under pressure attains a predetermined maximum.

5. In a gear pump, a body provided with a cavity therein and an inlet port and an outlet port leading into said cavity, two gear members in mesh mounted for rotation within said cavity, a third member independent of said body provided with a passage therethrough constituting such inlet port and with a face thereof including cylindrical portions in close proximity to the peripheries of the respective gear members and extending thereabout for a distance at least equal to the pitch of the teeth of said gear members whereby to form with said cavity and said gear members inlet and discharge chambers respectively communicating with said ports, said body being formed with a passage leading to such discharge chamber, one of said members being movable along a path transverse to the axis of one of said gear members, a plunger reciprocable in such passage in said body and connected to said movable member for moving the latter relative to the other members to form a leakage space between such face and at least the peripheral portion of one gear member and thus establish direct communication between the inlet and discharge chamber, and spring means associated with said plunger operative to resist movement of said plunger in one direction by pressure of fluid in such discharge chamber.

6. In a gear pump, a body provided with a cavity therein and an inlet port and an outlet port leading into said cavity, two gears in mesh mounted for rotation within said cavity, a member independent of said body provided with a passage therethrough constituting such inlet port and with a face thereof including cylindrical portions in close proximity to the peripheries of the respective gears and extending thereabout for a distance at least equal to the pitch of the teeth of said gears whereby to form with said cavity and said gears inlet and discharge chambers respectively communicating with said ports, at least one of said gears being mounted for movement transversely of its axis away from the portion of said face in close proximity therewith to establish direct communication between such chambers through the space thus formed between such portion of said face and the periphery of the movable gear, and fluid pressure responsive means operatively connected to said movable gear thus to move the latter, said fluid pressure responsive means being exposed to fluid under pressure delivered by said pump and operative to move said movable gear as aforesaid when such fluid under pressure attains a predetermined maximum.

'7. A pump according to claim 6 further characterized in that said fluid pressure responsive means comprises a bushing engageable with said movable gear and rotatable about an axis eccentric thereto, a third gear having a non-rotatable connection within said bushing, and a reciprocably mounted rack in mesh with said third gear, said rack having a portion thereof exposed to fluid under pressure delivered by the pump and being movable in one direction by fluid under pressure applied thereto whereby to rotate said third gear and thus said bushing to move said movable gear.

8. A pump according to claim 4 further characterized in that said third member is movably mounted in said body, said body and third member include shoulder portions which are in engagement with each other to position said face of said third member in close proximity to the peripheries of said gears, spring means are provided between said body and said third member yieldably holding said shoulder portions in engagement, and said fluid pressure responsive means exposed to fluid under pressure delivered by the pump constitutes a portion of said third member and is movable in opposition to the pressure exerted by said spring mean to effect separation of said shoulder portions and movement of said face away from said position with respect to the peripheries of said gears.

9. A pump according to claim 8 further characterized in that said body is counterbored to form such shoulder therein, and in that said body is formed with a passage leading from the discharge side of the pump to the shoulder in said body whereby fluid under pressure in excess of that exerted by said spring on said third member and acting on the shoulder of the latter is operative to separate said shoulders and thus to move the face of said third member away from the peripheries of said gears.

10. A pump according to claim 8 further characterized in that said body is formed with a passage leading to such discharge chamber, a plunger is reciprocable in such passage in said body, a link is connected to said plunger for effecting movement of said third member in response to movement of said plunger, and spring means bears upon said plunger to resist movement of said plunger in one direction by pressure of fluid in such discharge chamber.

11. A pump according to claim 10 further characterized in that said third member and said body are formed with interengaged shoulders positioning the face on said third member in close proximity to the peripheries of said gears, and said spring means yieldably holds such shoulders in engagement.

JAMES P. JOHNSON.

REFERENQES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 345,969 Harrold July 20, 1886 367,374 Deming Aug. 2, 1887 (Other references on following page) Number Dillon Aug. 26, 1947 Number FOREIGN PATENTS Country Date Great Britain Aug. 9, 1917 Switzerland May 1, 1935 Great Britain Aug. 12, 1926 Germany Sept. 7, 1924 Germany Feb. 8, 1936 

